Abstract The goals of this study are to produce and to characterize bio-oil from pyrolysis and distillation of liquid samples in a microwave reactor. Waste cooking oil (WCO) and fresh cooking oil (FCO) were employed as the feedstocks. A 900 W microwave reactor was modified and filled with 300 g of charcoal. It was used for both pyrolysis and distillation experiments. The pyrolysis experiments were performed at various feed flow rates and temperatures ranging from 0.051 kg/h to 0.306 kg/h and 400 °C–550 °C, respectively. The sample was introduced continuously into the microwave reactor for 60 min. Nitrogen gas was also supplied to ensure pyrolysis condition. The bio-oil product was then distilled to obtain fuel fractions. The results showed that the products yield and bio-oils composition were strongly influenced by pyrolysis temperature and type of cooking oils, while there was almost no influence of feed flow rate under the investigated condition. The bio-oil contained 90−100 wt.% aliphatic hydrocarbons and the rest were aromatic hydrocarbons. The bio-oil produced from WCO contained more than 50 wt.% green-diesel (C10-C15) which was comparable to that from FCO. The green-diesel fraction showed good fuel properties agreement to that of fossil diesels. Overall, microwave-assisted pyrolysis and distillation processes are potential ways to convert problematic WCO into useful liquid bio-fuel and green-diesel fuel.